摘要:
基于密度泛函理论的第一原理,计算了锡基无铅焊点界面常见的金属间化合物Cu6Sn5和Ni3Sn4的平衡晶格常数、合金形成焓以及弹性常数,分析了结构稳定的电子机制.结果表明,Cu6Sn5较Ni3Sn4合金形成能负,因此Cu6Sn5在热力学上更稳定,其合金化能力也较强.在力学性能方面,两相均属脆性相,表现出弹性各向异性,而Ni3Sn4的键合作用较强,弹性模量、剪切模量均大于Cu6Sn5,但Cu6Sn5表现出更好的塑性.从电子结构的角度,Cu6Sn5的成键主要来自于Cu原子d,p轨道与Sn原子p杂化,而Ni原子d轨道与Sn原子p轨道的强烈杂化作用是Ni3Sn4成键的主要原因.
Abstract:
Cu6Sn and Ni3Sn4 are important intermetallic compounds(IMCs), which were known to greatly improve the reliability of the soldered joints.In this paper, the first-principles calculations were performed to determine the stable structure of Cu6Sn5 and Ni3Sn4 IMCs.The structural and electronic properties of Cu6Sn5 and Ni3Sn4 IMCs were calculated.The results of energy calculation and density of states demonstrate that Cu6Sn5 IMCs have a more stable structure than Ni3Sn4.The results also show that they are exhibit anisotropy in elastic modulus.Moreover, the Ni3Sn4 shows more strong bonding effect and exhibits greater elastic modulus.However, Cu6Sn5 performs better in plastic, which is expected to account for the improvement in the reliability of the soldered joint.
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